“One Day” tracks the crisscrossing fates of two good-looking people from 1988, when they are newly fledged, happily drunken university graduates, to a point just short of the present, which is to say middle age for them. The movie’s conceit, embedded in the title, is that all of the depicted action takes place, from one year to the next, on a single date, July 15.

Being British, the two main characters — their names are Emma and Dex, and they are played by Anne Hathaway and Jim Sturgess — identify that square on the calendar as St. Swithin’s Day, which their American Gen-X counterparts may be more likely to know from the lovely, lovelorn Billy Bragg song of the same name.

As far as I could tell, that tune is not heard on the soundtrack, though much else is, including a lush, swooning, deliciously anachronistic orchestral score by Rachel Portman and a handful of period-appropriate numbers. By the final credits, as a song by Elvis Costello drowns out the snifflings of the audience — late-season allergies? mourning for lost youth? (spoiler redacted?) — the structural principle of the movie may at last become clear. Though it was adapted from a best-selling novel (by David Nicholls, who wrote the screenplay), “One Day” is less a conventional story than a mixtape.

This does not strike me as entirely an accident, or a wayward interpretation on my part. Nor is it entirely a bad thing. The fondly pirated compilation of moods and messages gleaned from vinyl and committed to cassette — that’s right, kids, they were actually, physically tapes back in the old days — may be the emblematic artifact of the generation to which Emma and Dex belong. And as it traces the orbit of their devoted friendship and almost-love, “One Day” turns an episodic story into an anthology of feelings and associations, many familiar, a few surprising, some embarrassing and one or two worth holding onto.

This makes it tricky to judge the film, directed by Lone Scherfig, as a whole, but easy to enjoy it in pieces. To recast the metaphor for the current era, it may even be desirable to reshuffle the tracks to suit diverse sensibilities. Did you like “When Harry Met Sally”? (Now is not the time to act all cool and artsy. I know you did. I saw you there.) Well, “One Day” is like a cover version played by a clever British pop band, hitting the theme of platonic male-female friendship (and the supposed long-term impossibility thereof) in a different tempo and key.

Or perhaps you were a fan of “Four Weddings and a Funeral.” (You’re on your own there, though I’m grateful that it briefly revived interest in W. H. Auden’s poetry.) “One Day” traffics in the same breezy, inviting Anglo-ness, finding charm in London’s gray weather and gentle comedy in the residue of the class system. It also has three weddings and two funerals, though most of the rites take place off screen.

As does nearly everything in Emma and Dex’s lives. Now and then — early and late — something momentous happens on July 15, but for the most part it is an ordinary day, and we glimpse only a piece of it, the year signaled by numerals on the screen. Some years are skipped over altogether, and others are indicated by a few seconds of actions: an unanswered phone call; a dive into a swimming pool. When we do linger with Emma and Dex, separately or together, some discreet exposition catches us up on what we need to know.

It starts in a rush of youthful sexual ardor, as the two of them, thrown together after a night out with friends, tumble back to Emma’s room as dawn approaches. Though they will remember this not-quite tryst as a “near miss,” it cements an affection that waxes and wanes over the years. Will they at last become lovers or allow their connection to lapse, awaiting the invention of Facebook?

This simple question generates quite a bit of curiosity and suspense, but “One Day” is at its best — observant, relaxed, touching and charming — when the central couple are apart. As they make their way through professional ups and downs and serious relationships with other people, the movie opens up and allows its attention to wander into odd corners and byways, encountering vivid, fully dimensional minor characters along the way. Among these are Ken Stott and Patricia Clarkson as Dex’s parents, and Rafe Spall and Romola Garai as the poor souls who would appear, on paper, to be perfect matches for Emma and Dex.

When those two are together, much is made of their contrasting temperaments and backgrounds. She is bookish, serious and comes from a (never seen) family of modest means, while he is dashing, irresponsible and wealthy. Mr. Sturgess does what he can to make you stop thinking about Hugh Grant, while Ms. Hathaway once again demonstrates her ability to be more appealing than her attractive co-star and more fascinating than her picturesque surroundings. (See also “Love and Other Drugs” and the most recent Oscar broadcast.)

Ms. Scherfig, a veteran of the Danish Dogme 95 movement, whose previous English-language films are “Wilbur Wants to Kill Himself” and “An Education,” can be a wonderfully centrifugal director, wandering away from the center of a conventional narrative toward its scruffy margins, where the interesting stuff happens. Her eccentric eye and offbeat rhythm sustain “One Day” through its stretches of banality and mitigate some of its flaws. Among these are a superficial sense of history — remember how girls used to wear their hair? remember nuclear disarmament? — and, more seriously, a late, disastrous dive into the deep end of weepitude.

In deference to the spoiler-sensitive, I’ll tread lightly here, but what happens near the end of “One Day” is likely to have a decisive effect on your opinion of the movie. Perhaps you will have seen this climax coming all along, and maybe you will find it splendidly moving. On the other hand, you might cringe to see the film’s wit and delicacy ruined by maudlin excess and wish you could remix the tape to get rid of that song you always hated.

“One Day” is rated PG-13 (Parents strongly cautioned). A bit of sex, and much discussion of and desire for same.

One Day

Opens on Friday nationwide.

Directed by Lone Scherfig; written by David Nicholls, based on his novel; director of photography, Benoit Delhomme; edited by Barney Pilling; music by Rachel Portman; production design by Mark Tildesley; costumes by Odile Dicks-Mireaux; produced by Nina Jacobson; released by Focus Features.